His Monday visit comes after a particularly violent weekend in the nation's third-largest city. Police say four people were shot and killed between Friday afternoon and Sunday night on Chicago's South and West sides. More than 30 others were wounded.

Since last year, Mayor Rahm Emanuel, Illinois' two U.S. senators and others have called on federal law enforcement to do more to combat violence in Chicago.

The head of Chicago's FBI office, Robert Holley, has said that about 25 percent of Chicago agents already work violent-crime cases.